Across the country, dozens of their colleagues in the Ahmadiyya Muslim Youth Association were doing the same at national parks closed or partially closed by the shutdown. They cleaned up litter, emptied garbage cans and swept the grounds — from the Everglades National Park in Florida to Joshua Tree, California and the Cuyahoga Valley, Ohio.The group hit the National Mall in Washington on Sunday morning. "Service to our nation and cleanliness are important parts of Islam," said Dr. Madeel Abdullah, president of youth group, in a press release. "We could not sit idly by as our national parks collected trash. We will lead by example and dispose of this garbage appropriately and invite all Americans to join us in these parks and others across the nation."Group members were joined by people from the general public who contacted the group through social media, spokesperson Salaam Bhatti told CNN, adding that the response to their efforts has been "overwhelmingly positive."Bhatti said members regularly participate in community cleanups, carried out as part of their faith. The group has logged almost 200,000 hours in clean-up projects since 2016, according to Bhatti. The Ahmadiyya Muslim Youth Association is the largest of its kind in the US, with more than 70 chapters and 5,000 members, all males aged 7 to 40.Bhatti said more than 60 percent of Americans do not personally know a Muslim, and community efforts like these increase dialogue with members of other religious groups."I hope it shows that we're not here just to talk about Islam the whole time," Bhatti said. "We're here to be part of America." National Parks have been largely closed to the public since the shutdown began December 22. In a press release Sunday, the National Park Service said it had "explored a number of options to address the maintenance and sanitation issues that have arisen at a number of highly visited parks," and will now use fee revenues to clean up trash and restrooms."We are taking this extraordinary step to ensure that parks are protected, and that visitors can continue to access parks with limited basic services," the statement said.Bhatti told CNN that if the shutdown continues, they will be looking for other national parks to help clear and for more ways they can help community members affected by the shutdown.An important part of Islam is to help "wipe away the tears of our neighbors during time of distress," he said. "We are humbly serving our nation at a time when many tears are being shed."